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Lithiation Mechanism of Tunnel‐Structured MnO 2 Electrode Investigated by In Situ Transmission Electron Microscopy
Author(s) -
Lee SeungYong,
Wu Lijun,
Poyraz Altug S.,
Huang Jianping,
Marschilok Amy C.,
Takeuchi Kenneth J.,
Takeuchi Esther S.,
Kim Miyoung,
Zhu Yimei
Publication year - 2017
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.201703186
Subject(s) - materials science , anode , electrochemistry , electrode , battery (electricity) , transmission electron microscopy , cathode , lithium (medication) , manganese , nanowire , nanotechnology , chemical engineering , metallurgy , chemistry , medicine , power (physics) , physics , quantum mechanics , endocrinology , engineering
Manganese oxide (α‐MnO 2 ) has been considered a promising energy material, including as a lithium‐based battery electrode candidate, due to its environmental friendliness. Thanks to its unique 1D [2 × 2] tunnel structure, α‐MnO 2 can be applied to a cathode by insertion reaction and to an anode by conversion reaction in corresponding voltage ranges, in a lithium‐based battery. Numerous reports have attributed its remarkable performance to its unique tunnel structure; however, the precise electrochemical reaction mechanism remains unknown. In this study, finding of the lithiation mechanism of α‐MnO 2 nanowire by in situ transmission electron microscopy (TEM) is reported. By elaborately modifying the existing in situ TEM experimental technique, rapid lithium‐ion diffusion through the tunnels is verified. Furthermore, by tracing the full lithiation procedure, the evolution of the MnO intermediate phase and the development of the MnO and Li 2 O phases with preferred orientations is demonstrated, which explains how the conversion reaction occurs in α‐MnO 2 material. This study provides a comprehensive understanding of the electrochemical lithiation process and mechanism of α‐MnO 2 material, in addition to the introduction of an improved in situ TEM biasing technique.